will the wall be free-standing, or will it retain soil alongside a bank, or will it enclose a soil-filled bed?

The free standing wall will be the hardest to create with enough soil and moisture inside the wall to enable plant growth, the other options are simpler.
Let us know which option you want to work with.

Thanks for replying to me! A part of the wall will enclose a narrow (about 3 feet) flower bed. Behind that flower bed that I am planning looms a cliff that's getting eroded, with two nice pines growing on it and keeping that cliff with their roots, apparently.
Another part of the wall will replace the existing low brick wall and will be at an obtuse angle to it. This existing low brick wall is a retaining wall. Behind it is a hill. Good soil gets washed down the hill all the time, and so behind that retaining wall some good soil has accumulated. So whatever I am trying to plant on that hill grows best near that retaining wall.
We don't have any rain in summer, so I can only plant drought resistant plants. On the hill we do have some irrigation, but I cannot install any more irrigation in this new flower bed I am planning. We are very close to our water limits in summer. At the moment what I have on the hill is iceplant and some baccarus bushes.

where can I get the June Sunset mag? Tried in our area in diff places. daniel